1. Field of the Invention
The present invention is an improved hemispherical sundial with improvements relating to versatility and ease of manufacture, installation and use.
2. Description of the Prior Art
Sundials indicating local apparent time have been used for thousands of years. A hemispherical sundial indicating civil or mean time was patented by O'Sullivan in 1927 (No. 1,651,621). O'Sullivan told how his sundial could be installed to correct for the difference between local and zone time, but his invention provided no indicia for installation. Also the O'Sullivan sundial was designed to face the celestial equator, which means only twelve hours of time indication would be possible, thereby causing a significant loss of time indication after sunrise and before snuset in the summertime at higher latitudes.
In 1988 a patent application was filed by the present inventor for a cylindrical sundial having installation indicia.
Also recently several instruments have been patented for sighting the site "solar window" and determining the times the sun's rays will be obstructed at the site.